This invention relates to the field of aspirating liquid from containers. In particular, this invention relates to the field of so-called “pick-up tubes” which are adapted to cooperate with a vacuum source or pump to aspirate the contents of a liquid-filled container through the top of the container.
In many technical disciplines, it is desirable to aspirate liquid from a container through the container's opening, which is usually located at or near the top of the container. As shown in FIG. 7, apparatus for performing this task commonly comprises a pick-up tube assembly T which can be releasably connected to a container C and coupled to a vacuum source V. The pick-up tube assembly usually comprises an elongated tube 10 (shown substantially enlarged for the sake of illustration) and some screw-on mechanism 11 for coupling the tube to the opening A of the container. The tube length is often fixed, being selected to approximate the vertical distance D between the container's opening and its bottom B. A portion of the tube's upper end 10A extends through a circular disk 14 which forms a part of the pick-up tube assembly and serves to suitably position the pick-up tube in the container's opening. Disk 14 has a diameter which is slightly greater than the diameter of the container's opening, whereby the disk may rest upon and be supported by the rim 16 of the opening. Disk 14 is usually clamped in place atop the opening by a threaded cap 18 which engages threads formed in the exterior of a short tubular section 19 surrounding the opening. The tube's upper end 10A is adapted to engage a flexible conduit 15 through which liquid in the container can be aspirated by the vacuum source or pump. Ideally, the length of the tube inside the container is selected so that the tube's lower end 10B rests on the container bottom when disk 14 is clamped in place atop the container by cap 18. As shown in FIG. 7, a small notch 22 is often formed in the bottom of the pick-up tube to enable liquid at the container bottom to enter the tube. Alternatively, a head is placed on the bottom of the pick-up tube which provides openings for liquid to enter the pick-up tube.
From FIG. 7, it will be appreciated that the length of the pick-up tube inside the container must vary to assure the complete emptying of containers of different height. If the tube length is too short, the lower end of the tube will not reach the container bottom, and the container cannot be emptied; if the tube is too long, disk 14 cannot be properly seated on and connected to the container top. A typical solution to this problem is to provide a pick-up tube assembly where the pick-up tube is operable to vary in length to accommodate different sized containers. With such an assembly, the same pick-up tube assembly may be changed from one container to another with relative ease. This is possible because many containers are made with a standard sized opening designed to receive a standard sized pick-up tube assembly. An example of a pick-up tube assembly with a pick-up tube of variable length is shown in U.S. Pat. No. 5,769,284.
When a pick-up tube assembly is changed from one container to another container after the liquid is consumed, or for any other reason, the assembly may not be cleaned during the transition between containers. In these situations, a user often removes the pick-up tube assembly from the first container and lays the pick-up tube assembly on a surface before it is placed in the second container. This exposes the pick-up tube to contamination from the surface on which it is laid. Even if the pick-up tube assembly is not laid on a surface, the pick-up tube is at least exposed to the open air when transitioning from one container to the next, and this also exposes the uncovered pick-up tube to contamination from the open air. In many environments, such as the clinical laboratory, contamination from the pick-up tube assembly can have a negative impact on processes being conducted, and may result in skewed or false test results. Accordingly, it would be desirable to provide a pick-up tube assembly operable to avoid contamination of the pick-up tube when the pick up tube assembly is transitioned between containers.